Surface contactor for blast cleaning machine



March 24, 1959 H. HASTRUP ET AL SURFACE CONTACTOR FOR BLAST CLEANING MACHINE 2 Sheets-Sheet 1 Filed March 4, 1957 FMS. 2

' INVENTOR. f/[flM/M/ M45 77? UP 20.4; c. mama/p 4 TOK/VE) March 24, 1959 H. HASTRUP ETAL 2,878,624

SURFACE CONTACTOR FOR BLAST CLEANING MACHINE Filed March 4, 1957 2 Sheets-Sheet 2 INVENTOR. HAW/ 44M HA'JMUP BY 1901; (I #457701 United States Patent SURFACE CONTACTOR FOR BLAST CLEANING MACHINE Herman Hastrup, Kaneohe, Oahu, Territory of Hawaii, and Rolf C. Hastrup, Pasadena, Calif.

Application March 4, 1957, Serial No. 643,866 8 Claims. (Cl. 51-11) This application is a continuation-in-part of our copending application, Serial, Number 555,495, filed December 27, 1955, now issued Patent No. 2,830,408, dated April 15, 1958.

This invention relates to grit blasting apparatus for cleaning surfaces, in which apparatus there is directed from a nozzle toward said surface a stream of air and abrasive material and from which surface the spent abrasive and debris is withdrawn in a stream of air through a confined passageway, said nozzle and said passageway being positioned in a housing generally termed a blast head or operating head. More particularly it relates to a surface contactor device adapted to contact an area of surface being cleaned and to serve as a connecting means between said blast head and said area of surface.

In abrasive blasting machines of the type above referred to, an object sought is to conduct the blast cleaning operation while keeping the abrasive, dust and debris confined so that there is no spattering of dirt and dust upon surrounding fixtures, and the clothes of the operator are kept clean. The operation is adapted for indoor work and to the surfaces of objects of varying size, including relatively small objects.

To conduct such an operation it is necessary that the surface contactor do more than simply contact the surface to be cleaned. It must encircle and confine an area of said surface which is immediately undergoing being cleaned, and it should effectively enclose and seal oif the space between the nozzle head and said area of surface, within which space the blast stream impinges against said area and the suction stream picks up the spent abrasive and debris and draws them away from said area. It is therefore desirable that the surface contactor be non-air pervious so that there may be no leakage or abrasive or dust to the surrounding space and no leakage of air from the outside into the blast area, either through the material comprising said surface contactor or underneath the edge of the surface contactor.

In United States Patent 2,723,498 issued to Hastrup and Pinkerton, and in our co-pending application Serial No. 521,719 filed July 13, 1955, now issued Patent No. 2,840,955, dated July 1, 1958, there are described portable blast cleaning machines of the type hereinabove referred to and having non-air pervious surface contactors, the material comprising the surface contactors there described being generally continuous or in one piece. countered on many objects to be cleaned, ditficulty is frequently encountered in maintaining a seal between the edge of the surface contactor and the surface being cleaned when the enveloping wall or skirt of the contactor is in one continuous piece.

It is an object of this invention to provide a non-air pervious surface contactor for abrasive blast cleaning machines of the above described type which permit of Because of the irregularity of the surfaces ensubstantially complete contact against irregular surfaces along the entire peripheral boundary line of the immediate working area of the surface undergoing treat ment to substantially seal said area and the spaceibetween the nozzle head of said machine and said area of surface against the passage of dust or abrasive to thesurrounding space or the infiltration of air from the surrounding space.

Another object is to provide a surface contactor adapted for blast cleaning a surface which lies in the corner formed by two intersecting surfaces. jects and advantages of the invention will appear from the ensuing description and the appended claims.

One form of the invention is illustrated by way of example in the accompanying drawings and is described in detail hereinafter. The particular constructions herein shown and described are to be construed as'illustra tive only, and not as limiting the invention.

In the drawings; Fig. 1 is a longitudinal sectional view of a preferred form of our surface contactor shown in place on one type of nozzle head of an abrasive blasting machine of the type above referred to, a fragmentary sectional view of said nozzle head being shown. T

Fig. 2 is a bottom plan view of the device shown'in Fig. 1. 1

Fig. 3 is a part side view and part longitudinal sectional view of a modified form of surface adapter, which is adapted for cleaning surfaces in corners where'two a floorand a wall.

surfaces meet at an angle, such as at the intersection of Fig. 4 is a bottom view of the device shown in Fig. 3,

through said inner channel toward a working area of the surface being cleaned, and spent abrasive is drawn away from said working area by a suction air stream through I said outer channel. The outer casing 10 extends axially outwardly beyond the end of said inner tube to form a rim 15. Preferably, said casings 10 and '11 aremade of abrasion resistant rubber and may be molded with spaced web members 16 (Fig. 2) positioned radially, between said inner and outer casings and integral with the walls thereof to give stiffness to said casings. The wall of the I outer casing 10, at and near said rim 15, is desirably of increased thickness to give adequate strength for the atr tachment thereto of the surface contactor, generally designated as 17. I

Corning now to the surface contactor, a metal collar or sleeve 18, adapted to snap over the rim 15 of the outer casing 10, fits into a recess 19 in the outer face of easing 10. Several laminae of rubber or similarly resilient material, 20 (three such laminae being shown in the drawcanizing or otherwise bonding the laminae to a collar of suitable material, which said collar may then be suitably fitted around the outer end of casing 10, such as the con struction shown in Fig. 3 hereinafter described. The said laminae are of sufiicient width that they extend a substantial distance axially beyond the end of said casing form a curtain or skirt which completely encircles and Patented Mar. 24, 1959 Other obenvelops .the space immediately beyond the end-of said outer ca sing 1ll. That, portion of each lamina which extends beyond its attachment to said outer casing is slitted axially a substantial distance from its outer edge to forrna multiplicity of .-fia ps 22. The flaps are so arranged thatthose in any given lamina overlap by a substantial distance the joints formed by the edges which face each other of .flaps in adjacent laminae. Thus, due to the flexibilityand resilience of the individual flaps, the multiplicity thereof and the joint breaking feature, when the;su rface contactor 17 is applied to an irregular'surface being cleaned, the segmented laminae effectively seal off the working area of said surface and the space between theiend of the nozzle head and said surface, both from leakage. of dust and abrasive to the surrounding space and from leakage of air from the outside into the blast area.

By way .offurther illustration of this device, ,and not to beconstrued asanylimitation to the scope of our invention, the following are measurements taken from devices which we have built and operated with very great successzgwitlrablast head having an outer casing ;10 of two and one-half inches outside diameter, the three laminae 20, each made of a conventional resilient rubber material, extended a distance of five-eighths of an inch beyond thecollar 19 and were slitted to provide flaps 22 approximating one-half inch in length and one-quarter inch in width. With surface contactors having but two of the laminae 20, we have employed flaps ranging .in width from eleven thirty-seconds to thirteen thirty-seconds of an inch.

Themumber of laminae employed may vary depending upon their thickness, the flexibility and resilience of the material of which they are made, their thickness, the width of the flaps, the shape and size of their cross-section, and the like. With flaps which are relatively narrow, it is desirable that a greater number of laminae be employed than when the flaps are of greater relative width. The rim v or other member employed against which the laminae are supported, should extend down near enough to where the flaps begin to prevent the unslitted portion of the laminae from collapsing under the force created by the vacuum within the space surrounded by the laminaei The flaps have sufiicient surface area that when the surface contactor 17 is held against an irregular surface so that the flaps are distorted from their normal position the area of surface contact between .flaps in adjacent laminae is eifective to seal the contactor against the passage of air either outwardly or inwardly therethrough. The outer ends of the laminae 20, which together form the mouth of the contactor, need not all lie in the same plane; nor need the outer edge or mouth of the contactor lie in the same plane. When desired the mouth may be either .convex or concave and may be made to conform to square corners or rounded surfaces. Surface contactors with different shaped mouths, and with the shape and dimensions of the flaps varying to some degree from each other, may if desired be made for use with surfaces of varying degrees of irregularity. One such contactor may be unclamped or otherwise readily removed from the blast head and another applied when the variation in surface irregularity makes such desirable.

In Figs. 3 and 4 there is illustrated a form ofsurface contactor adapted foruse in corners where the area to be cleaned lies at thesintersectionof, and in one or both of two surfaces. In this structure, the blast head with its outer casing :10, innercasing 11, inner channel 12, and outer channel 13, is essentially the same as that shown in Figs. 1 and 2, except that the outer end of outer casing 10isessentially of uniform external diameter and, therefore,.does nothave the recess 19.0f the outer casing shown in Fig. l. A shell, preferably of metal, designated generally as 30, is made up of an upper cylindrical portion 31, which serves as a collar detachably secured around the outer end of outer casing 10, and allower portion 33 which is desirably elliptical in cross-section, but may be of any 4 oval-like or otherwise smoothly curved elongated crosssection, and which extends axially beyond the outer end of casing 10, the said upper cylindrical and lower elongated portions being joined together by the part 32 which extends inwardly (preferably, though not necessarily, radially) where the cross-section of the elongated section is narrower than that of the upper or cylindrical portion. The shell 30 serves to hold the surface-contactor as a whole rigidlyin shape and permits the surface contactor to be conveniently removedfrom the outer casing 10 for replacement with other surface contactors adapted for the same or different types of surfaces. The outer end or edge 33' of the elliptical shaped portion 33 lies approximately in two oblique planes, shown in the drawing as at an angle of degrees from each other, whose line of intersection lies in the axially outward projection of the major axis of the said elliptical portion, or of the longest axis of the elongated portion 33 when it is not a true ellipse. Around the outside of the elliptical or elongated portion 33 of said shell are cemented or otherwise bonded thereto laminae 34 of rubber or similar material, the outer ends of which extend a relatively short distance beyond the outer edge 33' of said elliptical portion 33, to form a short skirt extending-therefrom. The outer edge of each of said laminae is cut so that it lies in two oblique planes which are parallel to the aforesaid oblique planes in which lies the edge or outer end 33 of the elliptical portion 33 of said shell 30, thus forming the skirt which extends downwardly or outwardly from said elliptical or elongated portion 33 with two oppositely positioned points 35 at the extremities of the longest axis of said elliptical or elongated portion. Being formed into this shape the edge of the skirt made up of said laminae will seek and contact the two intersecting surfaces when the surface contactor is held thereagainst. At and near the said two oppositely positioned points, the said laminae are slitted to form a series of axially extending flaps 36 disposed so that they break the joints between the flaps of adjacent laminae. The number of laminae, their width, the number and size of flaps therein, and other characteristics of both laminae and flaps and their arrangement, conform substantially to the laminae 20 and flaps 22 as hereinabove described for the surface contactor shown in Figs. 1 and 2. On objects having welded joint construction, a bead of the weld metal often exists in the angle or corner where the two surfaces are joined, so that with a surface contactor having its outer or contacting end comprised of the continuously extending material heretofore used it is often difiicult and sometimes impossible to form a seal between the contactor and the surface along the entire periphery of the area undergoing treatment. With the use of the said flaps in the said laminae this difficulty is very substantially overcome. If desirable, the flaps 36 may be formed-in the'laminae atother than at or near the points which fit into the apexof the angle formed by the intersecting surfaces, and may in fact, if desired, exist along substantially the entire edge (outer end) of the surface contactor. If the inner surface of the elliptical or elongated portion 33 of the shell 30 is desirably protected from abrasion by having a layer of rubber 37 cemented or bonded thereto. Desirably, though not necessarily, a rubber covering 38 is cemented around the cylindrical portion 31 of thesaid shell, and is of suflicient width to extend downwardlyover the upper portion of the laminae 34, thereby also coveringthe inwardly extending portion 32 of said shell 30.

By having the lower portion 33 of, shell 30 elongated in cross-section, as compared with its being circular in cross-section, and having the two points 35 where the line of intersection of the two oblique planes intersects the outer or working edge of the surface contactor, it is easy to hold the device in the correct position as it is moved in a direction in and along the corner between two intersecting surfaces. Moreover, the elliptical or elongated cross-sectional shape enables the. surface contactor to be used in corners having shorter sides than if it were cylindrical.

The major axis of the elliptical portion (or the longest cross-sectional dimension of the otherwise elongated portion 33) may vary within rather wide limits; and there is no fixed ratio between the length of such longest dimension and the length of the minor axis or shortest crosssectional dimension of the said elongated portion 33. Ordinarily the major axis should be sufiiciently long to afford ample area of the region just outside the area of surface which lies in the direct path of the blast stream (and within the periphery of the surface contactor) in order for the exhaust stream, which starts at the surface being cleaned, to carry away the spent abrasive and reduced in length, as in instances when the surface contactor is narrow so as to be adapted for use in corners formed by narrow surfaces, the major axis or longest dimension will be increased in length to give the areas 39 sufiicient size to afford satisfactory exhaust streams. The shorter the minor axis, the more versatile will be the surface contactor for use in narrow corners, and the minor axis can be reduced in length to the point where the blast stream may even impinge against the inside surface of the contactor in the region of its narrowest width, so that in that part of the surface contactor there is no area for suction stream and starting space for the available suction stream is all supplied at the said areas 39. If the parts subjected to the blast stream'are made of rubber, they do not wear rapidly. We have found that a generally satisfactory surface contactor for many corner surfaces encountered is had when the minor axis is reduced to a length such that the blast stream barely clears the inside surface of the contactor at its narrowest width and the major diameter is slightly longer than the outside diameter of the blast head to which the contactor is secured. A factor favoring a long major axis is that the farther the working or contacting edge of the surface contactor is from the center of the blast area, the less will be the force and intensity with which the ricochetting material tends to break through the seal effected by the skirt of the surface contactor and the contactbetween its working edge and the surface undergoing treatment. On the other hand, longer major axes render it more difficult to bring the instrument effectively close to obstructions which some surfaces being cleaned present.

It will be clear that a surface contactor of the foregoing type is adaptable for use in corners where the angle is greater or less than 90 degrees, by having the outer end 33' of shell 30 and the working edge of the skirt in conformity with such other angles; also that the angular and elliptical features, as described, may be employed with surface adaptors having a working edge comprised of a continuous material, in contrast to the laminae and flaps of the foregoing description, for use where the surface to be cleaned is smooth enough to permit such a working edge.

As has been pointed out, the fitting of the surface contactor to the outer casing of the blast head of the blast cleaning machine, is somewhat dilferent in the device illustrated in Figs. 3 and 4 from that of Figs. 1 and 2. Either or any other suitable manner of fitting may be employed. The sliding or frictional fit employed in the device of Figs. 3 and 4 makes it easier to replace the surface contactor. Moreover, the overall size of the device is less than with that of Figs. 1 and 2, thereby making the device more accessible for close and tight working areas. It will be clear that the laminae of the type shown in Figs.

1 and 2, whereinthe working edge lies in one plane, may be bonded to-a cylindrical or ring-like shell member substantially as the laminae are bonded to the elliptical por tion'33 of shell 30 in Figs. 3 and4, and that such cylindrical shell member may be adapted to fit slidably and removably over the outer casing 10 of the blast head of the machine,'the same as cylindrical portion 31 of shell 30 in Figs. 3 and 4 fits over the said outer casing 10.

As brought out in the foregoing description, the lower portion 33 of shell 30 may, in transverse cross-section, be elliptical or otherwise elongated and smoothly curved in outline, with a major and minor width corresponding to the major and minor axes when the cross-sectionis that of a true ellipse. In the claims appended hereto the term elliptical and other such terms referring to an ellipse are used to designate and embrace either of these forms of construction.

While we have shown a preferred form of our invention, it is to be understood that various changes may be made in its construction without departing from the spirit of the invention as defined in the appended claims.

We claim:

1. In an abrasive blast cleaning machine, an operating head provided with a channel through which a blast stream is directed toward a work surface and a channel through which a suction stream draws spent abrasive and debris away from said surface, said operating head being provided with a surface contactor for contacting and confining an area of said work surface when said area comprises two intersecting surfaces which form a corner,

- and to envelop and enclose the space between said operating head and said area of work surface through which the said blast stream is directed toward said area and said suction stream draws the spent abrasive and debris away from said area, said surface contactor comprising a hollow shell, said shell having its upper portion formed into a collar adapted to be detachably secured around the outer end of said operating head and having its lower portion oval in transverse cross section and coaxial with said collar portion, the terminal peripheral edge of said oval portion lying in two oblique planes which intersect in a line that lies in the path of said blast stream when said collar portion is secured around the outer end of said operating head and said blast stream is being operated.

2. The apparatus of claim 1 in which said oblique planes intersect in a line that lies in the space bounded by an axially outward projection of said collar.

3. The apparatus of claim 1 in which said lower portion of said shell is elliptical in cross section.

4. The apparatus of claim 3 in which said oblique planes intersect in a line that lies on an axially outward projection of the major axis of said elliptical lower portion of said shell.

5. The apparatus of claim 3 in which the major axis of said elliptical lower portion of saidshell is approximately equal to the diameter of said collar.

6. The apparatus of claim 1 with the addition of a skirt member secured to the outer end of said oval shaped lower portion of said hollow shell and extending axially outwardly therefrom and having its terminal peripheral edge lying in two oblique planes parallel respectively to said first mentioned oblique planes to constitute a working edge of said surface contactor.

7. The apparatus of claim 6 in which said skirt member comprises a plurality of laminae of flexible, resilient material, said laminae being positioned radially with reference to each other and unsecured to each other throughout a substantial part of their lower widths, and each lamina being slitted axially a substantial distance from its unsecured edge to provide a multiplicity of flat axially extending flaps, the adjacent flaps in each of said laminae having the adjacent edges thereof in abutting relation and the slits therebetween overlapped by flaps 2,878,624 7 3 in another lamina to render said skirt substantially im- References Cited in the file of this patent pervious to the passage of air from .the surrounding space UNITED STATES PATENTS into the blast area and from the blast area into the .surrounding spam 2,455,514 Mead Dec. 7, 1948 8. The apparatus of claim 7 in'which the said resilient 5 2,494,773 Mead Jan. 17, 1950 material is rubber. 8 Ha trup Nov. 15, 1955 

